The present invention relates to the repair of turbine engine components, and in particular to the repair of small diameter holes located on the flange of a part such as the forward inner nozzle support.
During operation of a turbine engine, the forward inner nozzle support can be damaged. Repairs must be done to the nicks and surface imperfections caused during normal operation. One common repair is cracks that emanate from the small diameter holes on the front flange of the forward inner nozzle support.
There are many techniques known in the art for repairing larger diameter holes, such as bolt holes about 0.30″ or greater in diameter. As shown in FIG. 1, in one such prior art repair, an area on a line about 45° on either side of the radial center line RC of hole 11 is removed. This material is then replaced with wedge 13 constructed of a similar material as the base material of the part being repaired. Wedge 13 contains at least two sides 17, 19 that are at approximately 90 degrees to one another. The remaining geometry of the wedge is not critical to the repair, and the remaining side(s) 21, can be of varying shapes and angles. This approximately perpendicular corner is inserted into the area of removed base material, the corner mating with edges 23, 25 of the base material left on the part. Wedge 13 is surrounded by three runoff plates 27, 29, and 31. Additionally, a backing plate may be used in the repair. Thus, five separate pieces are required to initiate the repair. Wedge 13 and run off plates 27, 29, and 31 are attached by tack welds 33 prior to initiating the repair. The multiple run off plates 37, 29, and 31 are small and difficult to assemble about wedge 13.
In the prior art repair, wedge 13 is welded into place with welds that are approximately 45 degrees from the original base material. In this configuration, the welds move the weld material (the weld zone with depleted material properties) outboard of the highest stressed areas at the hole location. This allows the raw material of the replacement wedge (with base materials properties) to remain in the highest stressed areas. The highest stressed areas surrounding the hole are located approximately 90 degrees from one another. This repair works well for holes down to about 0.30 inches in diameter, but on smaller holes the wedge becomes so small that the weld used to retain the wedge extends into the highest stressed areas of the flange. Prior to this invention, repairs to smaller diameter holes (i.e., holes having a diameter of about 0.30″ or less) on flanges were viewed as being unrepairable. Thus, a repair for smaller holes was needed.